Abstract

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Minimal residual disease (MRD) estimation can aid in clinical decision making. However, the lack of molecular markers precludes MRD estimation for most AML and many ALL patients. In the current study, we analyzed the potential of aberrant DNA promoter methylation as a biomarker for MRD in acute leukemias.For this purpose we used a novel quantitative real-time PCR method with bisulfite-treated DNA in more than 450 samples from patients with acute leukemias, other malignant diseases and controls. As expected, high levels of aberrant DNA methylation were specifically detected in patients with hematological cancers and especially acute leukemia. Importantly, a significant fraction of adult AML patient bone marrow samples in clinical remission were found to harbor increased levels of ERalpha and/or p15 DNA methylation. These DNA methylation levels were strikingly increased compared to normal controls and patients with non-malignant diseases. For patients with balanced translocations, a close correlation was found between fusion transcript levels (e.g. PML-RARalpha)and aberrant methylation levels. Importantly, 40% of the patients with increased ERalpha methylation relapsed within six months, whereas only 11% of AML patients with low methylation levels relapsed (p=0.007). In pediatric ALL patients, methylation MRD levels correlated closely with TCR/Ig MRD levels (r=+0.7, p<0.01). Our methylation MRD method successfully predicted 60% of the relapses, and no false positives occurred (Sensitivity - 60%, Specificity - 100%). In conclusion, analysis of meth ylation MRD (MMRD) status is a powerful novel biomarker for leukemia patients′ relapse risk. This MRD method is applicable to most if not all patients with hematological cancers.